Hi Debashis
I don't know whether you talk about PPDS heuristic or PPDS Optimizer
PPDS Optimizer move the order to others source of supply according to priorities ,please check SAP OSS FAQ note 1374824 FAQ - Order Creation PP/DS Optimization
Q13: How are Source of Supply priorities picked?
A13: Using the Procurement Priority in the header of the PPM or PDS.
Thanks
Regards